A Gradus

A <a href="https://en.m.wiktionary.org/wiki/handbook" title="handbook" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">handbook</a> used as an <a href="https://en.m.wiktionary.org/wiki/aid" title="aid" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">aid</a> in a difficult <a href="https://en.m.wiktionary.org/wiki/art" title="art" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">art</a> or <a href="https://en.m.wiktionary.org/wiki/practice" title="practice" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">practice</a>, specifically, a <a href="https://en.m.wiktionary.org/wiki/dictionary" title="dictionary" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">dictionary</a> of <a href="https://en.m.wiktionary.org/wiki/Greek" title="Greek" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">Greek</a> or <a href="https://en.m.wiktionary.org/wiki/Latin" title="Latin" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">Latin</a> <a href="https://en.m.wiktionary.org/wiki/prosody" title="prosody" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">prosody</a> used as a <a href="https://en.m.wiktionary.org/wiki/guide" title="guide" style="margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Lato, Helvetica, Arial, sans-serif; vertical-align: baseline; background: none rgb(255, 255, 255); color: rgb(107, 75, 161); hyphens: none;">guide</a> in writing of poetry in Greek or Latin.